Crop strippers

ABSTRACT

A crop stripper drum has a series of axial rows of flexibly displaceable teeth (12) circumferentially spaced around the drum. At the roots of the teeth are bulbous openings (12b, 22a) formed in metal members, which may comprise the teeth (12) or be elements (21) separate therefrom. For flexibility, the teeth may be given root openings larger than the openings formed by said separate elements, thereby reducing their root widths, or they may be put in a resilient mounting (62) that increases the deflection they experience under load. Separate elements (52) provided for forming the stripper openings, may be of an adjustable form to vary the width of the openings. The constructions disclosed are able to allow the use of metal for the active stripping means, whereby to increase the service life and reduce the power requirements. Adjustment of the size of the openings allows the striper to be adapted to harvest different crops.

This invention relates to crop strippers for detaching and harvestingcrops from standing plants. Such strippers are best known for strippinggrain from the heads of cereal crops such as wheat and herbage cropssuch as grass seed, but they can also be used to harvest crops such asrice, safflower, milo and peas, or to strip leaves, young shoots orblossom, for example, from the stems of crops.

WO86/01972 describes a crop stripper comprising a rotary drum which hasits axis of rotation extending generally horizontally and transverselyto the direction of advance through a crop. The drum is provided at itsperiphery with a number of axial rows or combs of projecting teeth atequispaced intervals about its periphery. As the machine advancesthrough a standing grain crop, the drum is rotated with its lowerperiphery turning in the direction of advance. The stems of the crop aretrapped in the spaces between the projecting teeth and as they are drawnaround the drum the grain is stripped from the heads of the plants.

The teeth are required to deflect easily, both to avoid damage fromcontact with obstacles or the ground, and to allow them to yield to theresistance of the plant stems through which they are drawn. On thataccount, it is customary to make the teeth of plastics. It is found,however, that they wear very rapidly when handling some crops andrequire frequent replacement because their stripping efficiency is thenaffected.

According to one aspect of the present invention, a stripper drum for acrop stripper has a plurality of axially extending rows of teeth, therows being mounted at spaced intervals about the periphery of the drumwith the teeth projecting outwards, and registering with said teeththere is a series of projecting elements of smaller radial extent, saidelements forming openings that register with the gaps between the teethat their roots.

With the teeth formed from a flexible plastics material, such aspolyethylene, and the projecting elements from an abrasion resistantmaterial such as metal, it is found that by shaping said openings tosubstantially conform with the gaps between the teeth or to overlap theedges of said gaps, it is possible to protect the plastics teeth againstpremature wear without in any way affecting their flexibility andoperating efficiency. The projecting elements can themselves be ofrelatively thin sheet metal because they can be protected againstexcessive bending loads by the flexible teeth.

Furthermore, although it has been found necessary in the past to formthe teeth of crop strippers' drums from plastics material in order togive them adequate flexibility it now is found that metal teeth can bemade sufficiently flexible, especially if the shape of the strippingopenings at their roots can be formed by the associated smaller radialelements, independently of the teeth themselves. The possibility ofmaking the teeth of metal brings the additional advantage that frictionfrom the crop is reduced and therefore the power requirement is reduced.

In some crops rigid teeth can be used because there is little or no riskof the teeth being overstressed: nevertheless there can be advantages insuch circumstances in providing the projecting elements as aforesaid, inregister with the teeth. Where flexibility of the teeth is significantit may be required to keep the width of the teeth small and it isdesirable that the metal itself should be capable of large elasticdeformations, e.g. being a spring steel. The limitation of the width ofa tooth is most effective in increasing flexibility if it is done at thetooth root, but that can increase the gap between the teeth to anundesirable extent from the point of view of stripping efficiency.However, the smaller elements can be formed with openings significantlysmaller than the gaps at the tooth roots and so provide the operativestripping surfaces in that region.

For grain stripping in particular, the flexible teeth preferably tapertowards their outer radial extremities so that the gap between themwidens towards their tips. But it is also preferred to form an increasedwidth gap at their roots, preferably with a bulbous gap profile. Acombination of these features gives the gap between a pair of teeth akeyhole-like shape.

The projecting elements preferably extend radially over the height ofsaid bulbous profile with the openings between them having acorresponding profile over that height. It is an advantage if theseoverlying elements continue radially outwards a short distance beyondthe bulbous profile and have a greater taper in this outer region thanthe taper of the corresponding portions of the flexible teeth, so thatat the tips of the projecting elements the profile of each flexibletooth extends laterally beyond the profile of its overlying projectingelement.

According to another aspect of the invention, a stripper drum providedwith a series of teeth and with supplementary smaller radial elementsassociated with the teeth is so constructed that there are separateattachment means for said teeth and said elements. Such an arrangementmakes it easier to replace the teeth and/or the elements when requireddue to wear or damage. The teeth can be grouped as a series on one ormore plates, whether metal or plastics, extending the axial length ofthe drum and the smaller radial elements can be similarly grouped.

To give the teeth a required degree of yielding under load, inparticular if the teeth are made of metal, they can be secured on thedrum through flexible mounting means, for example pads of a relativelysoft plastics material. Such mounting means can be arranged not only toallow greater displacement of the teeth but can also reduce stressconcentrations from bending loads applied to the teeth.

Since the formation of the teeth from metal can provide the improvedwear characteristics referred to above, the flexibility given by theflexible mounting means can make it possible to dispense with the seriesof projecting elements referred to above. According to a further aspectof the invention, therefore, there is provided a stripper drumcomprising a plurality of axially extending rows of teeth at spacedintervals about the periphery of the drum with the teeth projectingoutwards, flexible mounting means securing the rows of teeth throughradially inner portions thereof, said mounting means being deformable bybending loads acting on the teeth against the direction of rotation ofthe stripper drum to permit deflection of said inner portions under saidloads.

The invention will be described in more detail by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a broken-away end view of a stripper drum, in the direction ofarrow I in FIG. 2, with one of its sectors provided with leading shorterteeth in accordance with the invention,

FIG. 2 is a broken-away axial section on the plane II--II in FIG. 1showing the registering sets of teeth in that sector,

FIG. 3 is a fragmentary end view of another stripper drum according tothe invention in the direction of arrow I in FIG. 4,

FIG. 4 is a fragmentary front view of the drum in the direction of arrowIV in FIG. 3, and

FIGS. 5 and 6 are views similar to those of FIGS. 3 and illustrating afurther embodiment of the invention, and

FIG. 7 is a view similar to FIG. 3 illustrating another embodiment ofthe invention.

Referring to FIGS. 1 and 2, the drum has a central shaft or arbour 2through which it is supported on a harvesting machine, e.g. a combineharvester (not shown), and to which a rotary drive (not shown) isconnected. A series of triangular boss plates 4 are welded at intervalsto the shaft and have brackets 6 bolted to them. Bolted in turn to thebrackets are axially extending cover plates 8 forming the peripheralsurface of the drum body. The cover plates are each a Z-section membercomprising a main, generally tangential web 8a from which project a pairof shorter wings 8b,8c, the wing 8b at the leading edge of the web 8abeing directed generally radially outwards and the remaining wing 8cgenerally radially inwards.

The wings 8b,8c of adjacent cover plates lie opposed and parallel toeach other at a small spacing apart. In each of the spaces between thesewings a comb plate 10 is inserted and is secured between the coverplates by self-tapping screws 11. The comb plate, which is made ofpolyethylene, is formed with a series of outwardly directed teeth 12,the outer main portions 12a of which taper substantially to a point.Nearer the roots of the teeth the direction of taper is reversed and abulbous opening 12b is formed between each adjacent pair of teeth attheir roots. Such comb plates are well known and the gap profile hasbeen developed to promote efficient grain stripping from many crops, buthitherto the wear of the profile could be so severe that the efficiencyof operation cannot be maintained without frequent changes of the combplates.

In the present example, also secured to each cover plate 8, byself-tapping screws 18, is a protector plate 20 (only one being shown inFIG. 1) comprising a base portion 20a that lies against the cover plateand through which the screws pass, and a toothed profiled portion 20bhaving a series of radial projections or short teeth 21 that, in aposition of rest of the drum, lie against the front face of the adjacentcomb plate 10. For its greater part the toothed profile 22 of theprotector plate portion 20b corresponds to the root profile 12b of theplastics comb plate teeth it overlies. The tips of the projectionsextend a short distance beyond the bulbous root profile 22a and therethey have a profile different from that of the comb plate teeth. Theirtips 22b are in fact, more sharply tapered than the comb plate teeth.

In use, the drum is carried on a harvesting machine to travel from leftto right as seen in FIG. 1 while rotating in the direction indicated bythe arrow A. As the drum rotates each comb plate 10 descends into thegrain crop being harvested. In the movement of the comb plate throughthe crop, the stems of the plants are trapped between the teeth and aredrawn into the bulbous openings 12b,22a at the roots of the teeth. Therethe main stripping action takes place, and the grain is freed from theplants to be carried off by conveying means (not shown) and collected inthe machine in known manner.

During the operation of the machine, the plastics comb plate teeth canreadily flex if an obstacle is met or if the machine is travelling overuneven ground, and some flexure will also be induced by the resistanceof the plant stems. As the stems slide along the tapered main portions12a of the teeth they reach the bulbous openings 12b at the Foots andbearing contact is transferred to the profiled portion 20b of theprotector plate. Friction from the stems as the drum is driven throughthe crop now acts on the metal of that plate rather than the plastics ofthe comb plate. The bulbous profile of the openings at the roots of thecomb plate teeth can be maintained for long periods of use because ofthe greater resistance of the metal to rubbing wear. The flexibility ofthe comb plate teeth is completely unaffected but at the same time theyare able to help the metal teeth resist pressure loads and the protectorplate can be made of relatively thin sheet metal. The metal projectionsare also protected against impact from obstacles by the preceding combplate, the teeth of which act as an effective shield even when they aredeflected by an obstacle towards the protector plate so that there islittle danger of damage to the root gap profile from this source,

The increased taper at the tips of the metal projections reduces theexposure of the projections to any obstacles that pass between theplastics teeth, while at the same time they prevent the snagging ofplant stems that are sliding along the edges of the comb plate teethbehind them, even if those teeth are flexed away from the projections bythe friction loads from the crop.

The tapered sides of the plastics teeth are less effected by wear thanthe unprotected root openings would be, possibly because the stems canslide along the edges of the teeth. Indeed, close study indicates thatthe rapid wear previously suffered by the plastics comb plates at theroots of the teeth was more in the nature of ablation than abrasion. Theuse of metal for the protector plates, with its higher thermalconductivity, renders such an effect less likely.

In the embodiment shown in FIGS. 3 and 4, parts already described withreference to FIGS. 1 and 2 are indicated by the same reference numbers.In the space between each pair of wings 8b,8c the screws 11 now clamp asheet metal comb plate 30. Spacers 34 are also clamped by the screwsbecause the spacing between the wings is sufficiently large toaccommodate the thickness of a conventional plastics comb plate insteadof the metal plate illustrated. If that is not required, the wings 8b,8ccan be set closer together and the spacers 34 omitted. The comb plate 30comprises a series of outwardly directed teeth 36, the outer mainportions of which taper substantially to a point at their tips. Nearerthe roots of the teeth the width of each tooth is reduced considerablyby a bulbous opening 36a between adjacent pairs of teeth.

Mounted on each cover plate 8 is a supplementary metal protector plate40 having an angle-section comprising a base portion 42 secured againstthe cover plate by the screws 18 and a toothed profile portion 46parallel to the toothed comb plate 10 and having a series of radialprojections or short teeth 48 that are in register with the teeth 36 ofthe comb plate. The projections 48 of the supplementary plate arerelatively stiff compared with the comb plate teeth 36. As is clear fromFIG. 2, the size of the root openings 48a between the projections isconsiderably less than the openings 36a between the comb teeth and thematerial of the supplementary plate is more rigid.

The comb plates 30 and supplementary plates 40 are separately secured tothe stripper drum by the screws 11 or 18 respectively. These plates canbe removed and replaced independently of each other, so that maintenanceof the stripping drum is simplified.

During the operation of the machine the comb plate teeth 36 are intendedto flex readily over obstacles or due to the resistance of plant stemsthrough which they are moving. The tapered main portions of the teethguide the stems into the root openings 48a between the projections ofthe protector plate. The two sets of root openings 36a,48a may bedifferently shaped from each other because they are designed fordifferent functions. The openings of the protector plate, being smallerthan the root openings of the comb plate, exert a stripping action onthe plant stems and they can be shaped so as to optimise this function.In contrast, the larger openings 36a at the roots of the comb plateteeth do not influence on the stripping action and the openings can beformed primarily to give a desired degree of flexibility to the teeth.At their radially outer ends, the projections 48 have tapered side faces48b which can provide a relatively smooth transition for plant stemssliding over the tapered sides of the teeth 36 into the openings 48a.

In the example of FIGS. 5 and 6, the protector plate 40 is replaced by apair of overlapping plate members 50a,50b that cooperate to form thestripping openings. Each plate member has a series of spaced projections52, a profiled form being given to one side edge 54a or 54b of eachprojection, and the profiled edges 54a of one member being opposed tothe profiled edges 54a of the other member. The screws 18 securing themembers 50a,50b pass through elongated slots (not shown) in the membersso that they can be adjusted laterally of each other to place theopposed profile edges 54a,54b of each opening closer together or furtherapart. It is thereby possible to vary the width w of the strippingopenings by adjusting the positions of the members 50a,50b. It is knownthat the optimum dimensions of crop stripper teeth depend on theparticular crop being harvested and the arrangement of FIG. 5 and 6provides a ready way of adapting a stripper drum to harvest differentcrops without requiring additional resources. The arrangement isparticularly useful because of the ease with which the protector platescan be released.

As in the example of FIGS. 3 and 4 the profile at the roots of the teeth30 is not critical as long as it does not limit the range of adjustmentof the members 50a,50b. Also, although reference has been made to theembodiment of FIGS. 3 and 4 it will be understood that the teeth 30 ofthis modified construction can be of a plastics material.

In FIG. 7 a further embodiment of the invention is shown which issimilar in all unillustrated aspects to the embodiments alreadydescribed. In this case, a metal comb plate 60 is provided and has teethwith the same profile as the plastic comb plate 10 of the first example:that is to say the teeth have tapered outer portions to gather the cropand bulbous root openings to perform the main stripping function. As hasbeen mentioned above, such a metal comb plate does nor have sufficientflexibility to operate satisfactorily but in the present example thecomb plate 60 is sandwiched in the spacing between the wings 8b,8c witha thicker pad 62 of resilient material, e.g. of plastics, such aspolyurethane, or rubber. The screws 11 pass through rigid spacer tubes64 in the pad 62 to limit pre-compression of the pad. Preferably the pad62 has a Shore A hardness substantially in the range of 40 to 95,preferably 50 to 60. The spacing between the wings 8b,8c can beincreased to accommodate a greater thickness of resilient material,which the degree of cant applied to angled edge 66 of the wing 8c willalso influence the overall flexibility. The comb plate 10 is shownbutted against the front wing 8c to place the maximum thickness ofresilient material behind the plate but it is also possible to insertsome resilient material between the wing 8c and the plate 60.

In all the examples described herein the comb plates can be manufacturedin modular lengths so that they can be used to build up drums ofdifferent axial lengths. The protector plates can be simply produced inmodular lengths.

We claim:
 1. A crop stripper having a stripper drum provided with aseries of outwardly projecting crop-stripping teeth, said teeth beingarranged in a plurality of axially extending rows mounted at spacedintervals about the periphery of the drum, a series of projectingelements of smaller radial extent and leading said teeth arranged in acorresponding plurality of axially extending rows, the teeth of each rowof teeth and the elements of each row of projecting elements havingcorresponding pitches and being in alignment with each other, wherebyeach crop-stripping tooth has an inner portion behind a said elementaligned therewith and an outer portion projecting outwardly of saidelement, and said elements form openings that align with the gapsbetween the teeth at their roots.
 2. A crop stripper according to claim1 wherein the gaps between the teeth are at least substantially as largeas the openings between the elements.
 3. A crop stripper according toclaim 1, wherein said openings have a bulbous form with a maximum widthgreater than a radially outer entry neck of the opening.
 4. A cropstripper according to claim 1 wherein the elements have radially outerend margins which are overlapped laterally by the radially coincidentportions of the teeth.
 5. A crop stripper according to claim 1 whereinsaid projecting elements are provided on an angled plate having a firstlimb by which the plate is detachably secured to the drum and a secondlimb on which said elements are formed.
 6. A crop stripper according toclaim 1 wherein the teeth and the projecting elements have separateattachment elements to secure them to the drum.
 7. A crop stripperaccording to claim 1 wherein the teeth are held against resilientsupport means which are deformable by tangential loads on the teeth inuse.
 8. A crop stripper according to claim 1 wherein the teeth arearranged to be flexibly deformable away from the projecting elements inuse.
 9. A stripper drum for a crop stripper provided with stripper meansaccording to claim
 1. 10. A crop stripper having a stripper drumprovided with a series of outwardly projecting crop-stripping teeth,said teeth being arranged in a plurality of axially extending rowsmounted at spaced intervals about the periphery of the drum, a series ofprojecting elements of smaller radial extent and leading said teetharranged in a corresponding plurality of axially extending rows, theteeth of each row of teeth and the elements of each row of projectingelements having corresponding pitches and being in alignment with eachother, each crop-stripping tooth having an inner portion behind a saidelement aligned therewith and an outer portion projecting outwardly ofsaid element, and said elements forming openings that align with thegaps between the teeth at their roots, wherein the projecting elementsoverlap the edges of the teeth at their roots.
 11. A crop stripperhaving a stripper drum provided with a series of outwardly projectingcrop-stripping teeth, said teeth being arranged in a plurality ofaxially extending rows mounted at spaced intervals about the peripheryof the drum, a series of projecting elements of smaller radial extentand leading said teeth arranged in a corresponding plurality of axiallyextending rows, the teeth of each row of teeth and the elements of eachrow of projecting elements having corresponding pitches and being inalignment with each other, whereby each crop-stripping tooth has aninner portion behind a said element aligned therewith and an outerportion projecting outwardly of said element, said elements formingopenings that align with the gaps between the teeth at their roots, theopenings of said projecting elements being formed by respective groupsof elements providing opposite side edges of the individual openings,and said groups are relatively displaceable to vary the widths of theopenings they form.